So—the tiny bits of metal, the lock washers, are rather important to keeping the brakes actually on the truck. That’s why the previous post on lock-washer quality was worth the digression.
See, the twin bolts that pass through the body of the master cylinder, through the mount on the frame, and into threaded holes in a bar on the other side, are held tightly in place by a lock washer. A lock washer, for those who don’t know (or didn’t read the previous post), is essentially a nearly flat spring—a washer with a slit on one side and twisted slightly. When a bolt or nut is cinched down on a lock washer, the spring is pushed flat but pushes back against the head of the bolt to keep tension on it and prevent it loosening from the vibrations incident to driving.
The other working part is the mounting bar, a simple piece of steel with threaded holes in either end that acts like a double nut. Normally it would have just gone back on without a second glance, but in cleaning up the pieces after removing the master cylinder body a few months back I noticed that there was something stamped on the outside of the bar. Aha! The topic of another blog post!—and then I decided to just put it all together with the master cylinder.
To clean it up I used an old trick from woodworking: a three-dollar jug of acetic acid—plain white vinegar. This vinegar, however, I concentrated from 5% acidity to about 12% by simply setting the jug in the deep-freezer. The water freezes but not the acid, so simply pouring the not-frozen liquid into another container leaves a lattice of ice in the jug. Once that melts out, the concentrated acid goes back into the vinegar jug—properly marked, of course.
To clear the rust off the base metal I poured a bit onto a paper towel and then set the bar face down on it for about half an hour. A few quick strokes with the trusty wire brush revealled that the rust is not superficial and wouldn’t come off, despite my clever application of acetic acid. Oh well.
The stamp is nearly impossible to make out, but across the top of the circle can just be made out “MADE IN USA”. Right in the center is a four-digit number that I cannot quite read (probably a serial number for the part), and below that “DETROIT”. I’ll keep looking to see if I can find out what the serial number was.
Re-mounting the brake master cylinder itself was no problem. Here are shots of the mounting sequence, from cleared location to reattaching the brake line.
However, Green still does not have brakes. Why? Because while the cylinder has been rebuilt, the brake pedal has not yet been reattached and of course there is no brake fluid in the line. The rest of the brake system first needs to be checked for leaks, the wheel (slave) cylinders checked and perhaps honed. At least two springs need to be checked and cleaned or replaced. There is still lots to be done, but here is a visual before-and-after comparison.
Things do look a bit better, don’t they?